Background image doesn't show up
It is possible that the Source of the image is either incorrect, or you have changed the file location since making the .blend file. 


Press Nummpad 5 and then Numpad 1 to get into an orthographic view were the image would normally be view able from
Click on the folder icon next to the file location 
Find where the image is located and accept the location (make sure it is correct) 
Your image should now appear in the background of the scene